CompTIA Network+ Deploying and Configuring the DHCP Service

When would you use a Manual Allocation?

For terminals that must have a static IP address, such as Internet web servers.

Because the DHCP message's "sname" and "file" fields are rarely used today, what does the DHCP standard allow these fields to be used for today?

To contain options that do not fit in the standard "options" field.

What are the main disadvantages of a centralized DHCP infrastructure?

Traffic congestion Single point of failure

True or False? Member servers that have the DHCP role installed do not need to be authorized as this happens automatically.

True

True or False? When a client issues a DHCPREQUEST, it is trying to lease an IP address.

True

Are the DHCP options offered by Microsoft proprietary?

No. See RFC 2131

What is the importance of PXE?

(PXE) is a feature built into many network interface adapters that enables them to connect to a DHCP server over the network and obtain TCP/IP client settings, even when the computer has no operating system. Administrators typically use this capability to automate the operating system deployment process on large fleets of workstations. In addition to configuring the IP address and other TCP/IP client settings on the computer, the DHCP server can also supply the workstation with an option specifying the location of a boot file that the system can download and use to start the computer and initiate a Windows operating system installation. A PXE-equipped system downloads boot files using the Trivial File Transfer Protocol (TFTP), a simplified version of the FTP protocol that requires no authentication.

A client has reached T1 in its lease time of an IP address. What amount of time does this equate to on the client?

50% of the lease time which typically leases last 8 days, so T1 would be 4 days into the lease.

User Datagram Protocol (UDP) datagrams carry DHCP messages that are limited to how many bytes?

576 bytes

Which port does DHCP use on the SERVER?

67

Which port does DHCP use on the CLIENT?

68

What time value does T2 represent?

87.5% of the lease time which typically leases last 8 days, so T2 would be 6.75 days into the lease.

What is a Manually Allocated IP in DHCP also called?

A Reservation

What is another name for Manual Allocation?

A Reservation—In the Windows Server 2012 DHCP server.

If a client is in the "init" stage of DHCP negotiation what is its IP configuration?

At this stage it has no IP address. This is typical of the client as it boots for the first time on the network.

What is the reason for putting a reservation in DHCP?

A central record is created and accessible to all admins, without a risk of conflict occurring on the network

For a PXE adapter to access WDS images, the DHCP server on the network must have what?

A custom PXEClient option (option 60) configured with the location of the WDS server on the network.

What can test the limit of DHCP messages carried by User Datagram Protocol (UDP) datagrams?

A large number of options can test this limit.

Which of the following DHCP infrastructure designs requires the largest number of DHCP server implementations? a. Hybrid b. Centralized c. Dynamic d. Distributed

A. Hybrid

Your DHCP servers are burdened with heavy traffic, most related to IP address renewals. Unfortunately, virtually all the IP addresses in each of your subnets are allocated. Which of the following options is the best way to lower the renewal traffic? a. Increase the lease time. b. Deploy additional DHCP servers on the most burdened subnets. c. Shorten the lease time. d. Switch to manual allocation. *Select the BEST answer.

A. Increase the lease time.

You are preparing to deploy Windows 8 to a large number of new workstations. Which of the following options would be best? a. Install Windows 8 using Pre-boot Execution Environment (PXE) and Windows Deployment Services (WDS). b. Delegate the work to a team of local administrators to divide up. c. Manually install the operating system yourself. d. Manually configure each workstation's IP address. *Select the BEST answer.

A. Install Windows 8 using Pre-boot Execution Environment (PXE) and Windows Deployment Services (WDS).

Which of the following is a hexadecimal address that is uniquely associated with a specific Network Interface Card (NIC)? a. MAC b. JET c. BOOTP d. IETF

A. MAC

What servers should not be DHCP clients? a. Web servers, DHCP servers, and domain controllers b. Workstations c. End user laptops d. Computers, which might have IP addresses in the exclusion range *Select the BEST answer.

A. Web servers, DHCP servers, and domain controllers

A client fails to obtain a lease and returns to its "init" state (ie without an IP address), what happens next?

All TCP/IP communication then ceases, except for the transmission of DHCPDISCOVER broadcasts.

Explain Manual Allocation

An Administrator permanently assigns an IP address to a client computer from a scope.

For a stand-alone DHCP server to lease IP addresses, what action must an administrator take?

Authorize it. In the DHCP snap-in, right click and select Authorize.

Which of the following DHCP message types is sent first in process of obtaining an address lease? a. DHCPOFFER b. DHCPACK c. DHCPDISCOVER d. DHCPREQUEST

C. DHCPDISCOVER

Which of the following network components are typically capable of functioning as DHCP relay agents? a. Windows 8 computers b. Routers c. Switches d. Windows Server 2012 computers

B. Routers

A DHCP client first attempts to reacquire its lease at the half-way mark. This is known as? a. DHCP reservation b. T1 c. T2 d. DHCP lease

B. T1

Why must a DHCP server be placed on every subnet?

Because DHCP clients broadcast for a request in the discovery phase and broadcasts cannot go beyond the router.

At which layer of the OSI model does DHCP operate? a. Session layer b. Network layer c. Application layer d. Presentation layer

C. Application layer

Which of the following is not one of the techniques you can use to provide fault tolerance for DHCP servers? a. Splitting scopes b. Using stand-by servers c. DHCP servers using identical scopes d. Failover clustering

C. DHCP servers using identical scopes

Which of the following types of DHCP address allocation is the equivalent of a reservation in Windows Server 2012? a. Dynamic Allocation b. Automatic Allocation c. Manual Allocation d. Hybrid Allocation

C. Manual Allocation

Which of the following is an administrative grouping of scopes that is used to support multiple logical subnets on a single network segment? a. Host b. Scope c. Superscope d. Multinet

C. Superscope

One method a Dynamic Host Configuration Protocol (DHCP) server allocates IP addresses is called manual allocation. This process involves manually assigning an IP address to a particular server. What is the key benefit of DHCP manual allocation over manually configuring the address directly on the server? a. The DHCP server then contains a centralized list of permanently assigned addresses. b. The DHCP server might pass on more information than just an IP address. c. This process prevents accidental duplication of permanently assigned IP addresses. d. This manually assigned address is officially known as a reservation. *Select the BEST answer.

C. This process prevents accidental duplication of permanently assigned IP addresses.

Which of the following message types is not used during a successful DHCP address assignment? a. DHCPDISCOVER b. DHCPREQUEST c. DHCPACK d. DHCPINFORM

D. DHCPINFORM

To make use of Pre-boot Execution Environment (PXE) and Windows Deployment Services (WDS), what special configuration do you require on the server and client? a. The client must have a special PXE-enabled network adapter. b. Both client and server are capable by default. c. The client and server both require some preparatory configuration. d. The DHCP server on the network must have a custom PXE Client option (option 60) configured with the location of the WDS server on the network. *Select the BEST answer.

D. The DHCP server on the network must have a custom PXE Client option (option 60) configured with the location of the WDS server on the network.

What is a distributed DHCP infrastructure?

DHCP servers are placed on each subnet.

True or False? DHCP uses TCP as its transport protocol.

False. It uses UDP.

True or False? Microsoft recommends as good practice that a DHCP server should itself be a DHCP client.

False. The DHCP server must have a static IP address.

DORA

Discover Offer Request Acknowledgement

What are the three DHCP allocation methods?

Dynamic Automatic Manual

When the DHCP server sends a negative acknowledgement to the client that has requested an address, what MUST happen next?

If this happens, the client must initiate DORA.

What is the Powershell command to install the DHCP role?

Install-WindowsFeature DHCP [-ComputerName <computer_name>]

What device would eliminate the need for a DHCP server on each subnet?

Routers. Most IP routers have DHCP relay agent capabilities built into them.

What are the two types of scopes offered by DHCP?

Server option: Supplied to all DHCP clients receiving addresses from the server (eg: DNS address). Scope option: Supplied only to DHCP clients receiving addresses from a particular scope (eg: gateway address).

What is a centralized DHCP infrastructure?

Single DHCP server with relay agents to manage requests for subnets

What is the "magic cookie" field used for?

The "options" field in DHCP can contain many options, which would be impractical to define for each client, so this field informs the server about what is contained in the rest of the fields.

Explain Dynamic Allocation

The DHCP server assigns an IP address to a client computer from a scope for a specified length of time.

Explain Automatic Allocation

The DHCP server permanently assigns an IP address to a client computer from a scope.

What happens on the client when T2 is reached?

The client re-enters the "binding state." In practical terms, this means it begins the process of DORA—requesting an answer from ANY DHCP server.

How is the "magic cookie" designated?

The magic cookie, a 4-byte subfield, contains the dotted decimal value 99.130.83.99.

Give a disadvantage of a distributed DHCP structure.

The need to install and configure a large number of DHCP servers. This is especially true if you plan to have multiple servers on each subnet for fault tolerance.

What is the DHCP overload option?

This uses a so called "overflow" field that utilizes the redundant "sname" and or "file" fields if the option packet is over 576 bytes in length.

What is WDS?

Windows Deployment Services (WDS): Enables you to manage image files that remote workstations can use to start up and install Windows.

Which Microsoft program has a relay agent capability built into it?

Windows Server 2012. The DHCP relay agent capability is built into the Remote Access role.

Give 2 advantages of a distributed DHCP structure?

Your clients have ready access to their DHCP servers. You do not have to worry about DHCP traffic adding to the burden of your routers, because all the client/server traffic is local.

What is DHCPACK used for?

• DHCPACK: Used by servers to acknowledge a client's acceptance of an offered IP address

What is DHCPDECLINE used for?

• DHCPDECLINE: Used by clients to reject an offered IP address

What is DHCPINFORM used for?

• DHCPINFORM: Used by clients to obtain additional TCP/IP configuration parameters from a server

What is DHCPNAK used for?

• DHCPNAK: Used by servers to reject a client's acceptance of an offered IP address

What is DHCPOFFER used for?

• DHCPOFFER: Used by servers to offer IP addresses to requesting clients

What is DHCPRELEASE used for?

• DHCPRELEASE: Used by clients to terminate an IP address lease

What is DHCPREQUEST used for?

• DHCPREQUEST: Used by clients to accept or renew an IP address assignment

What is DHCPDISCOVER used for?

•DHCPDISCOVER: Used by clients to request configuration parameters from a DHCP server